Noun
freestream (plural freestreams)
English Wikipedia has an article on:freestreamWikipedia
The air far upstream of an aerodynamic body, i.e. before the body has a chance to deflect, slow down or compress the air.
Ramjet motors are also usually fitted with turbopumps, the turbine being driven either directly by external freestream ram air or internally by airflow diverted from combustor entry. Source: Internet
Second, the formation of strong shocks around aerodynamic bodies means that the freestream Reynolds number is less useful as an estimate of the behavior of the boundary layer over a body (although it is still important). Source: Internet
This increases the stagnation pressure recovered from the freestream and improves net thrust. Source: Internet